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Thursday, June 12, 2014

Rise and fall of prehistoric penguin populations charted

14 hours ago

A pair of Gentoo penguins. Credit: Gemma Glucas
A study of how penguin populations have changed over the last
30,000 years has shown that between the last ice age and up to around
1,000 years ago penguin populations benefitted from climate warming and
retreating ice. This suggests that recent declines in penguins may be
because ice is now retreating too far or too fast.

An international team, led by scientists from the
Universities of Southampton and Oxford, has used a genetic technique to
estimate when current genetic diversity arose in penguins
and to recreate past population sizes. Looking at the 30,000 years
before human activity impacted the climate, as Antarctica gradually
warmed, they found that three species of penguin; Chinstrap, Adélie and
southern populations of Gentoo penguins increased in numbers. In
contrast, Gentoo penguins on the Falkland Islands were relatively
stable, as they were not affected by large changes in ice extent.
A report of the research is published in the journal Scientific Reports.

Lead author of the paper, Gemma Clucas, from Ocean and Earth Sciences
at the University of Southampton comments: "Whereas we typically think
of penguins as relying on ice, this research shows that during the last ice age
there was probably too much ice around Antarctica to support the large
populations we see today. The penguins we studied need ice-free ground
to breed on and they need to be able to access the ocean to feed. The
extensive ice-sheets and sea ice around Antarctica would have made it
inhospitable for them.

A Chinstrap penguin. Credit: Dr Tom Hart
"What is particularly interesting is that after the ice age, all of these penguin populations
were climate change 'winners', that is to say the warming climate
allowed them to expand and increase in number. However, this is not the
pattern we're seeing today. Adélie and Chinstrap penguins appear to be
declining due to climate change around the Antarctic Peninsula, so
they've become 'losers'. Only the Gentoo penguin has continued to be a
'winner' and is expanding its range southward."

Dr Tom Hart of the University of Oxford's Department of Zoology, an
author of the paper, continues: "We are not saying that today's warming
climate is good for penguins, in fact the current decline of some
penguin species suggests that the warming climate has gone too far for
most penguins. "What we have found is that over the last 30,000 years
different penguin species have responded very differently to a gradually
warming world, not something we might expect given the damage current
rapid warming seems to be doing to penguins' prospects."

A group of Adélie penguins. Credit: Dr Tom Hart
To estimate changes in penguin genetic diversity, the researchers
collected feathers and blood samples from 537 penguins in colonies
around the Antarctic Peninsula. The scientists then sequenced a region
of mitochondrial DNA that evolves relatively quickly. Using the rate of
mutation of this region of DNA as a calibration point, the researchers
were able to chart how the size of these populations has varied over
time. The team working on the project included scientists from the
British Antarctic Survey and also US scientists from Oceanites Inc,
Woods Hole Oceanographic Institution, and the University of North
Carolina, Wilmington. "During the last ice age Antarctica was encircled by 100 per cent
more winter sea ice than today," says Dr Tom Hart. "As ice retreated,
these penguins had access to more breeding sites and more open ocean to
feed."